Abstract
Lead (Pb) is one of the most toxic and persistent elements, with no known biological role. High concentrations of lead enter saline soils through anthropogenic activities and industrial waste. The decontamination of Pb polluted sites through phytoremediation, especially by using woody plants, is an attractive approach. Eucalyptus camaldulensis is a good accumulator of Pb and a recommended tree species for reclamation of saline soils. However, there is very limited knowledge about the Pb-uptake behavior of Eucalyptus camaldulensis under saline conditions. The objective of this study was to examine the simultaneous impact of NaCl salinity and Pb stress on the phytoremedial potential and growth behavior of E. camaldulensis. Six-week-old Eucalyptus camaldulensis plants with uniform morphological features were transferred into hydroponic conditions, and they were exposed to the NaCl salinity stress at 200 mM and Pb stress at 10 mg L-1 and 20 mg L-1 (Pb1 and Pb2, respectively). The plants showed a 100% survival rate in all treatments. All the morphological parameters (plant height, plant diameter, and shoot dry weight) for E. camaldulensis were significantly affected when exposed to Pb or Pb + NaCl-salinity, with the exception of root length which was 36% higher in Pb2 as compared to the control. The Pb uptake (mg Pb plant(-1)) was much higher (49.3) under Pb2 + NaCl-salinity, as compared to the control (1.2) and other treatments, which shows that saline conditions increased the Pb-uptake in E. camaldulensis. The order of deposition of Pb (mg Pb kg(-1) of dry weight) in plant parts was root (103.4) >> shoot (17.5) > leaves (13.6). Similarly, the bioconcentration factor (BCF) of the roots was 4 to 6 times higher than shoot BCF.